Teleconferencing was introduced decades ago in a simplified form with picture telephones wherein bidirectional video and audio links were established between calling and called parties. With the advent of personal, desktop computers, teleconferencing has assumed a more complex form. Digital images such as text and graphics are displayed on each conferees display terminal while video images of the conferees are also displayed in a portion of the display. The latter display is made possible by positioning a camera to one side (top, bottom, left, right) of the display screen for recording images of the particular conferee viewing the display terminal. Since the conferee focusses attention on the screen and because the camera is positioned off to one side of the screen, eye contact is lacking between the conferee and the associated camera. This is known as a problem of parallax--a problem which arises whenever a camera must view one or more persons watching a display screen. Parallax is also a problem in the broadcasting industry where text prompting devices are employed.
From the perspective of the camera suffering a parallax problem, the conferee appears to be dozing when the camera is above the screen, gazing to the left or right when the camera is right or left of the screen, or looking at the ceiling when the camera is below the screen. As the conferee's scrutiny of the screen display becomes more close, the problem of parallax becomes more noticeable. Eye contact with the camera establishes eye-to-eye contact with each of the conferees shown on the display screen thereby creating a feeling of interest among the conferees. Similarly, a lack of direct eye contact with the camera causes a lack of eye-to-eye contact with each of the conferees shown on the display screen which, in turn, creates a perception of disinterest or preoccupation.
While some teleconferencing display terminals continue to be produced with an inherent parallax problem, conventional solutions have been proposed. One such solution involves the combination of a CRT display with a side-mounted camera focussed on the conferee through a properly angled beam splitter. Each conferee can concentrate on the display screen while maintaining eye contact with the camera. Although such a display terminal conquers the parallax problem, it cannot be overlooked that the cost of success is quite high. This display terminal is extremely bulky covering an area several feet square. This is a significant percentage of a standard desk surface. Bulkiness is an inherent problem caused by the introduction of a beam splitter.